1. Field of the Invention
This invention relates to film rewinding devices for cameras, and more particularly to film rewinding devices in cameras using 35 mm film.
2. Description of the Prior Art
In the cameras using 35 mm film, the exposed film must be transported back to the supply spool in the cartridge. For this purpose, provision is made of rewinding the film. This generally takes the form that a rewind release button is manually actuated and then a rewind crank is turned. In more detail, such camera as described above is provided with a rapid-winding lever, or an electric motor as a drive source which is drivingly connected to the film transportation mechanism, the charge mechanisms for the shutter, auto-focus and other mechanisms, and the one-frame advancement control mechanism. When in the winding mode, as the transport lever is cocked, or as the motor rotates, these mechanisms are driven to move and are reset so that the camera is ready for the next picture.
After the last frame of film has been exposed, the exposed film must be rewound before it is unloaded. In case where the rewinding is carried out manually, the rewind release button (R button) is pushed to release the film advancing mechanism from the connection with the film, and the rewind crank is then turned. In case where the rewinding is carried out using the motor, after the film advancing mechanism has been taken out of the connection by the rewind release button, a rewind start switch is operated to energize the motor, provided with the assurance that motion of the motor is transmitted to the supply spool in the cartridge.
Of such motorized cameras there is a type in which the drive source is constructed with only one motor, and the transmission of its motion is changed over from the winding drive system to the rewinding drive system, thus making it possible for the motor to suffice to selectively perform the winding and rewinding operations.
Even in the manual rewind type, a camera is also put into practical use that when the winding lever is turned in one and the same direction, winding and rewinding of the film are selectively effected, depending upon whether or not the rewind release button is actuated.
Such motorized or manual winding and rewinding selection drive type camera has a disadvantage that with the rewind release button (R button) unintentionally left pushed upwards, when winding is carried out, or with the R button arrested in the pushed position because of a malfunction, when winding is carried out, though the film remains stationary, the other mechanisms operate likewise as in the normal condition, with the result that a double exposure, or overlap of picture frames is caused to occur. Such situation reveals itself in almost similar outward appearance to that when the normal operation proceeds, and, therefore, the operator is not aware of it, continuing successive shooting with the production of a great failure.
Another disadvantage of the motorized winding and rewinding selection drive type camera is that since it is the common practice in the art that after the rewind release button is first pushed upward, a rewind start switch is closed to set the motor control circuit in the rewind mode, if the actuation of the R button is preceded by the closure of the rewind start switch by mistake, the film is teared at the perforations as it is perforce pulled while no longer advancing because of all film exposed, and in extreme case is cut off from the cartridge.
Still another advantage is that when the R button is taken out of the hold by some reason at a time during the rewinding operation, the camera is switched from the rewinding to the winding mode again.
To prevent this, in the conventional camera it is required that a mechanism be built in so that even when the rewind start switch is only turned on, the circuit is prevented from rendering operative. A further requirement is that a lock member be provided so that when the R button is pushed, it is held in the advanced position, and a member for releasing the R button from this locking engagement is also necessary to provide. This gives rise to an additional disadvantage that the apparatus is made very complicated, and the production cost is remarkably increased.
An object of the present invention is to eliminate the above-described drawbacks and to provide a device responsive to actuation of a rewind release button for cutting off the film advancing mechanism and the various charge mechanisms from the driving torque transmission system.
Another object of the present invention is to provide such an arrangement that a rewind switch remains locked from actuation until and R button is depressed, and after the rewind switch is once turned on, the R button is locked in the pushed position until that switch is turned off.
Other objects of the present invention will become apparent from the following description of an embodiment thereof.